What it does
Runs the image through an analog video synthesizer, bending and smearing it line by line like a warped broadcast signal.
FM, frequency modulation, is the same idea that carries radio: a steady carrier tone whose frequency is nudged up and down by another signal. Analog video artists have bent images this way since the 1970s, feeding a picture’s brightness into an oscillator and watching the screen dissolve into rolling lines. This effect ports that patch to the GPU, so the whole frame is modulated line by line the way a video synthesizer would do it in hardware.
The brightness of each pixel sets how fast the carrier wobbles as the effect scans across a row, and the demodulated result is drawn as a stripe wherever the wave crosses zero. Flat areas produce even, parallel bands; edges and detail crowd the lines into dense knots. Push the signal harder and the picture smears into pure interference; ease it back and a ghost of the original floats inside the pattern.
Because it is a real signal process, the character is in the tuning: line spacing, how strongly the image drives the carrier, and whether the bands bow, wave, or drift over time. You can split the channels so red, green, and blue modulate at slightly different phases and fringe apart, break the lines into dots and dashes, or rotate the whole scan. On video it animates like a live feed off a misbehaving deck.
Signature looks
Rolling broadcast
Even parallel bands drifting slowly up the frame with a faint image trapped inside them. A picture caught halfway through an analog transmission.
Circuit-bent smear
The signal driven hard until the lines knot and tear, colours splitting into red and blue fringes. The look of a video synth patched into feedback.
Contour map
Gentle spacing with the image barely modulating the carrier, so the bands trace the subject like elevation lines on a topographic map.
Try it on your own footage
This effect runs live in the Modulate editor, with layers, effect chains, masks, and keyframes. Free, no signup, nothing to install.
Common questions
What is the FM modulation effect?
It is a visual effect that treats an image as a signal and frequency-modulates a carrier wave with it, the same math radio uses for sound. The demodulated output is drawn as flowing lines and stripes whose spacing follows the brightness of the original, turning a photo or video into a pattern of bands.
Where does the analog video synthesizer look come from?
From artists working since the 1970s who patched image signals through modular video hardware, oscillators, and feedback loops, a lineage carried on today by makers like LZX and Syntonie. Bending a picture with an oscillator dissolves it into rolling lines, and that circuit-bent, signal-processed texture is what this effect recreates in software.
Is FM modulation the same as glitch?
They overlap but differ. Most glitch effects corrupt or displace pixels; FM modulation is a clean signal process that redraws the whole image as modulated waveforms. The result can look glitchy, but it comes from synthesis rather than from breaking the file, so it stays smooth and controllable.
Can I use the FM modulation effect on video?
Yes. The modulation is computed every frame, so the bands drift, wave, and re-form with the motion underneath instead of sitting as a static overlay. In Modulate it runs in real time in your browser and stacks with VHS, CRT, and other analog effects.
How do I get colour fringing in the pattern?
Offset the phase of the red, green, and blue channels so each one modulates slightly differently. The bands split into coloured fringes the way chroma separates on a mistuned analog signal, which reads as the classic video-synth rainbow.
Related effects
VHS effect
The full worn videotape package: color bleed, static, dropouts, wobble, and tracking errors.
NTSC effect
The look of an analog TV broadcast: soft edges, color bleed, scanlines, and signal noise.
CRT effect
The look of an old tube monitor: glowing phosphor stripes, slight color fringing, and a darkened vignette.
Datamoshing
Smears moving parts of the image into blocky trails, like a corrupted video that never gets a clean frame.